Flywheel generator for charging the capacitor of a capacitor discharge ignition system



.Feb. 24, 1970 c. L. SHANO E AL 3,496,920.

FLYWHEEL GENERATOR FOR CHARGING THE CAPACITOR OF A CAPACITOR DISCHARGEIGNITION SYSTEM Flled March 6, 1968 PULSE GEN.

LEVEL D51. 90

INVENTORS. DANIEL BOROVIK I CHARLES SHANO m W M ATTORNEYS.

United States Patent U.S. Cl. 123-148 4 Claims ABSTRACT OF THEDISCLOSURE The flywheel of an internal combustion engine has a ring gearabout the periphery of it which induces a voltage in a variablereluctance pickup. A rectifying circuit connects the induced voltage tothe ignition capacitor for charging the same after it has beendischarged in synchronism with the engine through the ignition coileither by the operation if conventional ignition points or through anelectronic trigger.

Background of the invention This invention pertains to a capacitordischarge ignition system for an internal combustion engine and moreparticularly to a unique device for charging the ignition capacitorafter it has been discharged.

In the past ignition systems where the ignition capacitor has beenelectronically discharged have been complicated by the fact thatcircuitry must be provided for charging the ignition capacitor frombattery potential. Furthermore, it is desirable that the energy storedin the discharge capacitor of the ignition system be independent ofbattery voltage. This is especially true in internal combustion engineswhich must operate continuously in remote areas such as along naturalgas or fuel oil pipelines. These engines in many instances are remotelycontrolled from a location some distance from the engine. They arestarted, for example, by a potential source coupled to the enginesdirectly from the central station. Their reliability, however, isreduced because of the dependence of the ignition system on localbatteries.

Summary of the invention It is an object of this invention to provide acapacitor discharge ignition system for an internal combustion engine inwhich the ignition capacitor is independent of any battery formaintaining a charge thereon.

It is another object of this invention to provide a capacitor dischargeignition system for an internal combustion engine which is relativelysimple and inexpensive to manufacture.

In one embodiment of this invention a capacitor discharge ignitionsystem for an internal combustion engine is characterized by a flywheelwhich has a ring gear about the periphery thereof and which is drivenpast a plurality of variable reluctance pickups to induce a voltage inthe pickups for charging the ignition capacitor. The variable reluctancepickups are connected in series to insure that there is suflicientinduced voltage at low engine rpm. to charge the capacitor. A Zenerdiode circiut is connected across the ignition capacitor to limit theinduced voltage from the pickups at high engine rpm. to preventexcessive charging thereof. The flywheel generator can be used in anignition system in which the ignition capacitor is discharged by theoperation of ignition points in the conventional manner, to provide apulse for gating on an electronic switch, which discharges the capacitorthrough the ignition coil. The flywheel generator can also be used in anignition system where both advance and distribution is providedelectronically. In one typical circuit, the flywheel in addition tohaving the ring gear around the periphery of it also carries a fluxvarying element. The flux varying element induces a voltage in amagnetic pickup, which rises to a given level at a rotational positionof the flywheel that varies in accordance with the speed of rotation ofthe same. A level detector is responsive to the voltage produced by thecoil at the given level to energize a pulse generator which operates asemiconductor trigger to discharge the ignition capacitor through theignition coil.

Description of the drawings FIG. 1 is a schematic wiring diagramillustrating an ignition circuit in accordance with this invention;

FIG. 2 is an expanded side elevation view of a portion of a flywheelgenerator in accordance with this invention; and

FIG. 3 is a schematic wiring diagram of a second embodiment of anignition circuit utilizing the principles of this invention.

Detailed description Referring to the drawing, FIG. 1 illustrates anignition system for an internal combustion engine, which includes anignition coil 10 having a primary winding 12 and a secondary winding 14.The secondary winding 14 may be coupled to the center post of adistributor as is wellknown in the art. A silicon controlled rectifier16 is connected in series with an ignition capacitor 18, which is acrossthe primary winding 12 of the ignition coil 10. A diode 20 is connectedacross primary winding 12 and serves to reduce the amplitude of currentreversals in the ignition coil secondary winding 14. This reduces theamount of electromagnetic radiation produced by the ignition coil andresults in a corresponding reduction in radio interference and noise.

Silicon controlled rectifier 16 is triggered in synchronism with theinternal combustion engine by pulses applied to the gate 16a thereof.These pulse are coupled to the gate 16a by means of a transformer 21having a secondary winding 24 coupled between the gate 16a and thecathode of rectifier 16. Transformer 21 has a primary winding 26 whichis connected through resistor 28 and ignition switch 30 to the battery32. The opposite end of the primary winding 26 is connected to ground byintermittently operable breaker points 34. Breaker points 34 may be thewell-known mechanical type breaker points synchronized with engineoperation. A diode 36 connected across primary winding 26 of transformer21 damps out reverse current transients.

When capacitor 18 is charged to the desired firing potential and siliconcontrolled rectifier 16 is fired by a pulse supplied to the gate 16a,capacitor 18 discharges through primary winding 12 of ignition coil 10.This produces a high voltage pulse in secondary winding 14, which isapplied to the distributor for igniting the fuel in the cylinders of theinternal combustion engine. Transients which could possibly fire thesilicon controlled rectifier 16 at the wrong time are damped out by thediode 36.

In accordance with the principles of this invention, a unique generatoris used to charge the capacitor 18 subsequent to it being discharged bythe silicon controlled rectifier 16 through the ignition coil 10, Thegenerator includes the engine flywheel 40, which is coupled to anddriven by the internal combustion engine. Position in a spaced relationto the flywheel 40 is a variable reluctance pickup 42. About thecircumference or periphery of the flywheel 40 is a ring gear 44 having aplurality of teeth. As shown in FIG. 2, the variable reluctance pickupincludes a plurality of magnets 46 interposed between core laminations48. Windings 50 are wound around the core laminations 48 so the inducedvoltage is additive and in a manner to connect the individual magneticpickups in series. The individual laminations 48 are spaced so that thechange of reluctance in each winding caused by flywheel rotation is inphase so that the output of the gen erator is the arithmetic sum of thevoltage induced in each winding. As the flywheel 40 rotates, the teeth52 of the ring gear 44 causes the reluctance of the flux path throughthe core laminations 48 to vary in a manner that produces a sinusoidalvoltage in the windings 50. The output from the pickup 42 is coupled bytransformer 54 to a full wave rectifier 56. The output of the rectifier56 is coupled by resistor 58 to the ignition capacitor 18. In someoperations, the transformer 54 can be eliminated, and the generator maybe such that a half wave rectifier can -be used without deviating fromthe scope of this invention.

It is necessary that the storage capacitor by fully charged from thefiring of one cylinder of the engine to the firing of the next cylinder,This means the flywheel generator must develop enough energy to chargecapacitor 18 in a portion of a revolution of the flywheel. This canvary, for instance, from one charge per revolution for a one cylinderengine, to two for a two or four cylinder engine, to four per revolutionfor an eight cylinder engine. Because the output voltage is dependent onthe velocity of the teeth past the pickup, it is necessary, in order toget suflicient charging potentials at a low flywheel r.p.m., to connectthe pickups in series as shown in FIG. 2. At high engine speed, however,it is necessary to limit the voltage output of the generator to avoiddamaging the ignition capacitor 18 with overvoltage. To accomplish this,a voltage limiting network 68 comprising three Zener diodes connected inseries is connected across the ignition capacitor 18. In a typicaloperating installation the charge on capacitor 18 is in the area of 400volts. It is, therefor, desirable to have the voltage limiting networkcalibrated to maintain the charge on the capacitor 18 substantially inthis area.

In operation, initial cranking of the engine during starting causes theflywheel 40 to induce a voltage in variable reluctance pickup 42 tocharge the ignition capacitor 18. During cranking the points 34 areclosed grounding the primary 26 of transformer 21. Subsequent opening ofthe points generates a pulse in secondary winding 24 of the transformerto trigger silicon controlled rectifier 16. Triggering of the siliconcontrolled rectifier 16 discharges the ignition capacitor 18 through theignition coil to produce a firing pulse for the engine. It can be seentherefore that compared to other more complicated networks for chargingthe ignition capacitor 18, the charging circuit of this invention isextremely simple and therefore relatively inexpensive to manufacture.

FIG. 3 illustrates another type of a capacitor discharge ignition systemusing the flywheel generator of this inven tion for charging theignition capacitor. The circuit shown is for use with a four cylinderengine with a four stroke cycle. Thus two cylinders will go throughtheir power stroke for each revolution of the engine flywheel. It is tobe understood, however, that this ignition system can be adapted toengines of other numbers of cylinders within the scope of the invention.Each of the cylinders of the engine is provided with a spark gap orspark plug 6265 and separate ignition coils 67-70. The secondarywindings of each of the coils are connected across their respectivespark gaps.

A silicon controlled rectifier 72 connects the parallel connectedprimary windings of the ignition coils 68 and 70 in series across theignition capacitor 75. Similarly, a silicon controlled rectifier 74connects the parallel connected primary windings of ignition coils 67and 69 in series across the ignition capacitor 75. Of the two cylindersassociated with the ignition coils 67 and 69, one is ready to be firedand the other is on its exhaust stroke. Thus, only the cylinder to befired is affected by the pulse through the ignition coils 67 and 69.This is also true of the ignition coils 68 and 70. Accordingly, twocylinders at a time are fired, one of which is on exhaust stroke andconsequently is not affected.

In this system, two magnetic pickup units 81 and 82 are used inassociation with a single flux varying element 83 on the engine flywheel85. As the flywheel 85 rotates, the flux varying element 83 will cause achange in flux in the windings 81 and 82 to generate a potentialtherein. The flywheel 85 rotates in a direction of the arrow in FIG. 3so the pointed end of the flux varying element 83 passes by the polepieces of the magnetic pickups 81 and 82 first. The space between theflux varying element 83 and the magnetic pickups 81 and 82 will decreaseat a gradual rate until the stepped portion 86 of the flux varyingelement passes by the pole piece at which time the gap closes rapidly.At slow speeds, i.e., low flywheel r.p.m., sufficient potential to causethe level detectors 90 and 91 respectively to conduct will not begenerated in the magnetic pickups 81 and 82 until the stepped portion 86passes by them. That point at which the level detectors conduct is whenthe generated potential in the magnetic pickups 81 and 82 exceed thebreakdown voltage of Zener diodes 93 and 93a. At higher speeds, andfaster rotation of the flywheel 85, a potential great enough to causethe level detectors to conduct can be generated in the magnetic pickups81 and 82 prior to the reaching of the stepped portion 86. The effecttherefore of the shape portion is to provide electronic spark advancefor the engine. An ignition system of this type is described in greaterdetail in Patent No. 3,356,896, issued Dec. 5, 1967 and assigned to theassignee of this application.

Conduction of the level detectors 90 and 91 applies a pulse to the baseof NPN transistors 96 and 96a of the pulse generators 98 and 99.Conduction of the pulse generators 98 and 99 alternately trigger siliconcontrolled rectifiers 72 and 74 to discharge the ignition capacitor 75.

The flywheel 85 besides carrying the flux varying element 83, whichprovides the firing pulses for the ignition cylinders and alsoelectronic advance, further carries a ring gear 100 around the peripherythereof similar to the ring gear 44 of the embodiment described inconjunction with FIG. 1. Also a variable reluctance pickup 102 similarto the variable reluctance pickup 42 described in conjunction with FIG.1 is positionedvin a spaced relation to the teeth 104 of the ring gear100. These two elements combine to form a flywheel generator forproviding a substantially sinusoidal potential, which is rectified inrectifier 106 and coupled by resistors 108 to charge the ignitioncapacitor 75 subsequent to discharge thereof. Also, as was shown in theignition circuit of FIG. 1, a voltage limiting circuit 110 comprisingseries connected Zener diodes is coupled across the ignition capacitor75 to limit the charge on that capacitor at high engine speeds.

The flywheel generator of this embodiment also provides anotherimportant feature. Connected across the output of the rectifier 106 arecurrent limiting resistor and Zener diode 117. Resistor 115 and Zenerdiode 117 form a step down voltage network for reducing the directcurrent output voltage of the flywheel generator from the rectifier 106to between 10 and 14 volts. The output of this step down network is usedto provide a DC potential through the resistors 120 and 121 for thedirect current circuit of pulse generators 96 and 96a.

The flywheel generator described in conjunction with this 1 embodimenttherefore not only greatly simplifies the circuit for charging theigintion capacitor 75, but, by providing the direct current for thepulse generators, makes the ignition system completely independent ofthe engine battery.

What has been described, therefore, is a relatively simple andinexpensive capacitor discharge ignition system for an internalcombustion engine in which the ignition capacitor is independent of theengine battery for maintaining a charge thereon.

What is claimed is:

1. In a capacitor discharge ignition system for an internal combustionengine, including trigger circuit means for discharging the capacitor insynchronism with the engine to produce firing pulses, the combinationincluding, a flywheel driven by the engine, a ring gear having aplurality of teeth, said ring gear being positioned about the peripheryof the flywheel, pickup means positioned in a spaced relation withrespect to said flywheel, said pickup means including a plurality ofcore laminations, a plurality of magnets interposed between said corelaminations, and a plurality of windings each positioned about a corelamination, said flywheel being driven past said pickup means with saidteeth of said ring gear causing the flux path through said corelaminations to vary in a manner to produce a voltage in said windings,said windings being series connected and positioned about saidlaminations so that the voltages induced in each winding are additive,and circuit means connecting said induced voltage from said pickup meansto the ignition capactor for charging the same subsequent to thedischarge thereof.

2. The capacitor discharge ignition system of claim 1 wherein saidcircuit means includes rectifier means and voltage limiting meanscoupled between said rectifier means and the discharge capacitor, saidvoltage limiting means acting to limit the induced voltage from saidpickup means at high engine rpm. to prevent excessive charging of theignition capacitor.

3. The capacitor discharge ignition system of claim 1 in which thetrigger means for discharging the capacitor in synchronism with theengine includes a silicon controlled rectifier having input, output andgate electrodes, and a pulse generating circuit connected to the gateelectrode which is responsive to the opening of engine ignition pointsto energize said silicon controlled rectifier, and wherein the ignitioncapacitor is connected to the input of said silicon controlledrectifier, and an ignition coil is connected to the output of saidsilicon controlled 6 rectifier so that said flywheel generates aninduced voltage in said pickup means to charge said capacitor with thesame being discharged through the ignition coil by said ignition pointsoperating to trigger said silicon controlled rectifier.

4. The capactor discharge ignition system of claim 1 wherein saidtrigger circuit means includes magneto pickup means including aninductance coil, level detector means, pulse generating means andsemiconductor trigger means connected in that order to the ignitioncoil, and wherein said flywheel has a shaped flux varying portionthereon, said flux varying portion producing a voltage in saidinductance coil which rises to a given level at a rotational position ofsaid flywheel which varies in accordance with the speed of rotationthereof, said level detector means being responsive to the voltageproduced by said inductance coil reaching the given level to energizesaid pulse generator means to operate said semiconductor means todischarge the ignition capacitor through the ignition coil, and saidring gear inducing a voltage in said pickup means to charge the ignitioncapacitor subsequent to the discharge thereof.

References Cited UNITED STATES PATENTS 359,552 3/1887 Bassett. 2,071,5732/ 1937 Randolph et al. 3,240,198 3/1966 London et al. 3,311,783 3/1967Gibbs et al. 3,326,199 6/1967 McMillen. 3,356,896 12/1967 Shano.3,358,665 12/ 1967 Carmichael et al.

LAURENCE M. GOODRIDGE, Primary Examiner US. Cl. X.R. 310; 315-209

